In general, vertical mixers for mixing and/or cutting bulk material use an auger positioned in a mixing chamber to mix and optionally cut the bulk material for output. The auger is generally powered using a motor provided by a separate vehicle, such as a tractor via a power takeoff. Regardless of power supply, a transmission or gearbox is used to transfer the output force from the motor to the auger. The gearbox comprises a plurality of gears, an output shaft and a number of bearings, all of which require lubrication using either oil or grease provided by a gearbox lubrication system. Typically, the gearbox is mounting in the floor of the mixing chamber and oriented in a vertical position within the auger tube of the auger. Two main current systems for oil lubrication are:                1) Open loop system shown in FIGS. 1; and        2) Closed loop system showing in FIGS. 2 and 3.        
Both systems make use of an external oil reservoir 30 with an oil fill line 35 that runs from the bottom of the oil reservoir 30 to the bottom of the gearbox 40. The open loop system leaves the upper breather port 85 of the gearbox 40 open to the environment and relies on the assumption that the oil level in the gearbox 40 will always stay below the level of the upper breather port 85. This level is referred to as the maximum oil level 70. This works in theory but becomes a problem in practice when you consider the location of the upper breather port 85. In general, the upper breather port 85 of the gearbox 40 sits only about 1.5″ above the upper oil lubricated roller bearing 55. This level is referred to as the minimum oil level 65. Since oil is needed to lubricate the upper roller bearing, the bearing should always be covered in oil and therefore the oil level fluctuation range is very small. It is therefore prudent that the fill level on the external reservoir 30 be placed at the same level as the breather port 85 on the gearbox 40 so that operator's do not risk letting the oil level fall below the upper roller bearing 55. This then becomes a problem because if the reservoir 30 is full, it is very likely that the oil level in the gearbox 40 is at or above the breather port 85, meaning the gearbox 40 may easily become air locked. Also, once the oil reaches the breather port 85, it is also likely that it will spill out of the gearbox 40 and possibly contaminate the environment. To deal with the spillage issue, it is possible to install a breather pipe 80 to the breather port 85. The breather pipe 80 is typically an elbow fitting with a short section of pipe extending upwards. If the oil reaches the breather port 85, it then has to travel up the pipe 80 before it can spill out of the gearbox 40. One problem associated with this arrangement and breather pipes in general, is that once the oil begins to travel up the pipe, the gearbox becomes air locked. Air locking of the gearbox typically occurs when the oil heats up and expands thereby increasing the oil level in the gearbox above the breather port 85. Oil then enters the breather pipe 80 and settles in a low point of the pipe 80. Once the oil contracts, any oil at a low point in the pipe is effectively stuck in the pipe and prevents air from venting from the gear box. The air locked gearbox is then prone to insufficient lubrication as well as inaccurate oil fill readings.
The closed loop system combats the spillage issue by running a return line 37 from the breather port 85 back to the top of the external reservoir 30. Therefore, if the oil level 15 inside the gearbox 40 reaches the level of the breather port 85, instead of spilling into the surrounding environment it will instead return to the external reservoir 30. However, the problem with air locking is still an issue with the closed loop system as oil spills into the return line 37 to a certain level 90. Further, because it is necessary to run the return line 37 externally between the gearbox casing and auger tube 25, there becomes a chance that the line 37 may be torn or damaged during operation, thus allowing oil to spill into the environment and allowing the gearbox 40 to seize. Closed loop systems although better for combating spillage are more prone to air locking as the return line typically includes a portion that is lower than the breather port 85 and therefore encourages the likelihood of air locking the gearbox.
A further problem associated with both the open loop and closed loop system is that the oil level 15 inside the gearbox 40 can surpass the maximum level in a number of instances. For example, the oil reservoir 30 may be overfilled 16. Accidental over or under filling is easily done as the difference between the maximum and minimum oil level is small and accuracy of filling is low. The oil level may also surpass the maximum level if the gearbox may be inclined during use, again partially because the difference between the maximum and minimum oil level is small.
With regard to the grease lubrication system, one existing problem is with the grease fill line 45 being run externally between the gearbox casing and the auger tube 25. Only the top roller bearing 50 is greased, because it cannot be lubricated by oil. The top roller bearing 50 cannot be lubricated by oil because its proximity to the top of the gearbox 40 makes it essentially impossible to fit a breather in this region. Further it is difficult to ensure that the bearing 50 would remain submerged in oil at all times. As a result, grease is used to lubricate the top roller bearing via a grease fill line run 45 external the gearbox 40. However, by running a grease line 45 between the gearbox casing and the auger tube 25, there becomes a chance that the line 45 may be torn or damaged during operation, thus starving the upper bearing 50 of lubrication and possibly causing major damage to the gearbox 40 over time. Typically, a grease line protector weldment 60 is used to protect the grease line 45.
Cold weather can further increase the likelihood of damaging either of the grease fill line 45 or the oil fill line 35 as frost build up inside the auger tube can cause the lines to freeze to the auger tube and break.
A need therefore exists to provide a gearbox system have a lubrication system comprising a breather that overcomes or mitigates at least one of the problems associated with gearboxes as outlined above or as known in the art.